Greatest bass line ev'ah. Follows chord pattern to "Imagine" (you can play this bass part under the verse of latter). Of course the "ching" at the start is from Pink Floyd. Paul was at Abbey Road during 'Dark Side' sessions and did a voice over.

The critics despised this one for two reasons.(1) It's by McCartney, and they normally would lambaste anything he did. Perhaps they expected better from him.(2) It's a light bubblegum type of song. A genre which is universally loved by us mindless masses but hated by the music elite.

But remember, it sold extremely well and was hummed by almost everyone. McCartney is the king of melody and this silly love song reflects it.